If you see the difference between the numbers
16, 91, 256
2^4, 3^4, 4^4

next difference should be 5^4 i.s. 625, thus the next number should be 354+625 => 979

To solve this, replace a n digit number by adding all digits, and solve, keep on repeating it until you get single digit.

10×11×12={(1+0)×(1+1)×(1+2)}^2 =6^2=36=3+6=9

11×12×13={(1+1)×(1+2)×(1+3)}^2 =24^2 =(2+4)^2=36=3+6=9

12×13×14={(1+2)×(1+3)×(1+4)}^2 =60^2 =(6+0)^2 =36 =3+6=9

13×14×15={(1+3)×(1+4)×(1+5)}^2 =120^2 =(1+2+0)^2 =9

14×16×20={(1+4)×(1+6)(2+0)}^2 =70^2 =(7+0)^2 =49 =4+9=13=1+3=4